sounds like either they were none eaters,imports non eaters, or just someone to pawn off the trouble snakes on a new guy. I contact the shop and point out if he willing to cover the gas you come out and help him set up a more proper tank/cage, and a show how to assist/force feed ( if you know how ) the snakes if you deem they may need it. I also give him any vet numbers that deals with reptiles in the area incase he wants to have them checks for parasites,worms and such cause who knows what they could picked up at the breeders or in the store..
I ask the following questions,
what chemicals used around them/in the store
what the bedding used
temps how measured and humidty
how he heating the cages( might be cooking them or freezing if the temp probes set in the wrong places )
I also would see what kind of shop it is incase you don't want to deal with him ( aka the shop a pack warehouse type were can bearly walk and if it clean or just a fly by night deal were he could be gone in 5 months or so.)
I personally don't sell, trade, or adopt out any snake I rescued,hatched or what ever unless it eating and the person has some proper snakes handling xp( I spent 7 hours with one girl that wanted a snake getting her use to handling picking up and such with different snake of mine befoer whe left with the pair she wanted ). I also (when working ) print out the basic info like temps, what safe /not safe to use for bedding( be shocked how often petstores tell people pine safe to use with snakes).
I also will email those that contacted me about questions to the site here and list books they could read to get more info.
I also give them my info and tell them I will take any snake back if it becomes too much for them to care for.